Structural member for furniture

ABSTRACT

A pedestal table has a column extended from a base for supporting a top in an elevated position. The column includes two identical column halves which are fitted back-to-back against each other, and the column halves have lugs and sockets positioned such that the lugs on one column half fit into the sockets on the other column half and vice-versa. U-bolts extend behind the lugs and have their threaded legs projected from the ends of the column to secure the column to the base and top.

United States Patent [191 Camilleri [4 1 Apr. 29, 1975 STRUCTURAL MEMBER FOR FURNITURE [75] Inventor: Charles F. Camilleri, Affton, Mo.

[73] Assignee: Gusdort' & Sons, Inc., St. Louis, Mo.

[22] Filed: June 1, 1973 [2!] Appl. No.: 366,992

[52] U.S. Cl. 108/150; IDS/153; IDS/158 [51] Int. Cl .t A47b 13/02 [58] Field of Search 108/88, I50, I53, 156, l08/l58, 56; 248/188.l;297/D1G. 2. 445, 452; 24/263 C [56] References Cited UNITED STATES PATENTS 923,795 6/1909 Koester 108/88 3,230.909 H1966 Watson......... l08/l53 3.698.150 Anderson........t...............::.. 297/452 3,757,03l 9/l973 lzraeli 24/263 C Primary ExaminerR0y D. Frazier Assistant E.\'aminerDarrell Marquette Attorney, Agent, or Firm-Gravely, Lieder & Woodruff [57] ABSTRACT A pedestal table has a column extended from a base for supporting a top in an elevated position. The column includes two identical column halves which are fitted back-to-back against each other, and the column halves have lugs and sockets positioned such that the lugs on one column half fit into the sockets on the other column half and vice-versa. U-bolts extend behind the lugs and have their threaded legs projected from the ends of the column to secure the column to the base and top.

14 Claims, 10 Drawing Figures AYENTEB Z SHEEI 10F 3 FIG.|

FIG.2

STRUCTURAL MEMBER FOR FURNITURE BACKGROUND OF THE INVENTION This invention relates in general to furniture and more particularly to structural members used in furniture.

With the rising cost of lumber, more and more furniture manufacturers are turning to plastics in the construction of furniture. The plastic is usually molded and colored to appear as wood so that the furniture so formed will harmonize with existing wood furniture. In the case of structural members such as columns and posts, the plastic is usually molded about a metallic member. which not only reinforces the plastic, but also serves as an anchor for bolts or other connecting devices used to connect the structural member to a base, top or other component. Indeed, one of the disadvantages of plastic has been its inability to firmly anchor such connecting devices.

Reinforcing the plastic with metallic inserts increases the cost of the structural member far above that if the member were formed entirely from plastic, since such a construction is more difficult to mold and assemble.

SUMMARY OF THE INVENTION One of the principal objects of the present invention is to provide a plastic structural member capable of being used as a post or column in furniture. Another object is to provide a plastic structural member which possesses high strength, yet has no metallic reinforcing. A further object is to provide a structural member of the type stated capable of firmly anchoring steel connecting devices such as U-bolts for securing the structural member to other components of furniture. An additional object is to provide a plastic structural member which is easy and inexpensive to manufacture. Still another object is to provide a plastic structural member of the type stated which is ideally suited for use as a column or post of a pedestal table or other table. These and other objects and advantages will become apparent hereinafter.

The present invention is embodied in a structural member having sections, one of which has a lug and the other a socket for receiving the lug so as to interlock the sections. A bolt projects from the column and is extended behind the lug. The invention also resides in a pedestal table utilizing the structural member as a column. The invention also consists in the parts and in the arrangements and combinations of parts hereinafter described and claimed.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the specification and wherein like numerals and letters refer to like parts wherever they occur:

FIG. I is a perspective view of a table provided with a column constructed in accordance with and embodying the present invention;

FIGS. 2 and 3 are sectional views taken along lines 2-2 and 33, respectively, of FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 2 and shows the two column halves interlocked at their lugs and sockets;

FIG. 5 is an elevational view showing the back side or inside of one of the column halves;

FIGS. 6, 7, and 8 are sectional views taken along lines 6-6, 7-7, and 88, respectively, of FIG. 5, and showing the U-bolts illustrated in dotted lines;

FIG. 9 is an elevational view showing the back side or inside of a modified column half; and

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9.

DETAILED DESCRIPTION Referring now to the drawings (FIG. 1), A designates a pedestal table which is ideally suited for supporting a television set, although it may be used for other purposes. The table A includes a base 2 which rests on the floor, a column 4 which projects upwardly from the base 2, and a top 6 which is secured to the upper end of the column 4 and supported in an elevated position thereby. The top 6 is seized to underlie a television set or any other desired object.

The base 2 may be molded from a plastic and is provided with an upwardly opening socket 10 (FIGS. 2 & 3) at the center thereof. The socket I0 possesses a rectangular shape and the bottom wall thereof is provided with bolt holes I2 (FIG. 2). One plastic suitable for the base 2 is structural foamed polystyrene, and this plastic should be shaped to the proper configuration by low pressure injection molding. The base 2 may or may not be provided with casters.

The top 6 may be made of wood, chipboard or any other suitable material possessing enough strength to support the desired object. The top 6 has two bolt holes 16 (FIGS. 1 & 2) near the center thereof.

The column 4 consists of identical shells or column halves 20 which are positioned back-to-back and attached together in that position. The column halves 20 are preferably formed from plastic, and one plastic which has been found ideally suited for this purpose is structural foamed polystyrene. This plastic is shaped into the configuration illustrated in drawings (FIGS. 5-8) by using low pressure injection molding techniques. When the column halves 20 are joined together, they interlock with and secure U-bolts 22 and 24 (FIGS. 2 & 3) firmly in place with the threaded legs of the U-bolt 22 projecting from the bottom of the column 4 and the threaded legs or shanks of the U-bolt 24 projecting from the upper end of the column 4. The lower end of the column 4 fits into the upwardly opening socket 10 in the base 2, and when so fitted the threaded legs of the U-bolt 22 align with and project through the bolt holes 12 in the bottom wall of the socket l0. Threaded over the ends of the U-bolts 22 are nuts 26 which secure the column 20 to the base 2. The top 16 rests on the upper end of the column 20, and the threaded legs of the U-bolt 24 align with and project into the bolt holes 16 in that top. Flanged nuts 28 thread over the legs of the U-bolt 24 and for the most part are disposed within the holes 16 of the top 6. However, the flanges of the nuts 28 overlie the upper surface of the top 6 and thereby retain the top 6 on the column 20.

Since the pedestal halves 20 are identical, they may be formed in the same mold. Each pedestal half 20 constitutes an integral molding and includes (FIGS. 5-8) a full front wall 30 having a decorative configuration molded on the outwardly presented face thereof. Along its sides the full front wall 30 merges into half side walls 32, and these walls also may have a decorative configuration molded into them.

Along the lower ends of the front and side walls 30 and 32, the column half 20 is provided with a shoulder 34 (FIG. 5) from which a tapered end portion 36 projects. The end portion 36 is tapered on all three lateral faces, that is on the faces located directly below the front wall 30 and the two half side walls 32, and this taper corresponds to the taper of the socket in the base I0. Indeed. the end portion 36 is sized to fit snugly in and to occupy one-half of the socket so that when two column halves are fitted back-to-back they will occupy substantially the entire socket 10. The lower end of the tapered end portion 36 is traversed by a lower cross wall 38 which forms the lowermost face on the column half 20.

The full front wall and the half side walls 32 extend to the very top of the column half 20 where they terminate in a flat supporting surface 40 (FIG. 5) lo cated in a horizontal plane which is perpendicular to the longitudinal axis of the column half 20. The underside of the top 6 is positioned against the surface 40 when the two column halves 20 are joined back-toback. Traversing the upper end of the column half 20 slightly below the flat supporting surface 40 is an upper cross wall 42 which is formed integral with the facing wall 30 and side walls 32.

Formed integral with and projecting rearwardly from the full facing wall 30, generally at the center thereof, is a spacer boss 44 (FIGS. 3 & 5) having an axial bore 46 extended entirely through it. The bore 44 is counterbored from both of its ends.

The backwardly or rearwardly presented faces of the side walls 32, the tapered end portion 36, the cross walls 38 and 42, and the spacer boss 44 all lie in the same plane which is parallel to the general plane of the front wall 30 and extends through the center of the column 4. These faces form a back abutment surface 48 (FIGS. 5-8) on the column half 20. Thus, when the two column halves 20 are placed back-to-back the corresponding back abutment surfaces 48 will abut along a parting line which is practically indiscernible.

The lower cross wall 38 is provided with notches 50 (FIGS. 5, 6 8t 8) adjacent to the tapered sides of the end portion 36, and the spacing between the two notches 50 equals the spacing between the threaded legs on the lower U-bolt 22. Indeed, the notches 50 are wide enough to loosely accommodate the legs of the U-bolt 22, while the depth thereof is slightly greater than the radius of the U-bolt 22.

Directly above the notches 50 the tapered end portion 36 is provided with backing ribs 52 (FIGS. 5-7) which are formed integral with the front wall 30 and side walls 32 and the distance between the ribs 52 and the notches S0 is substantially less than the length of the threaded legs on the U-bolt 22. When the U-bolt 22 is correctly positioned in the tapered end portion 36, the backing ribs 52 lie behind the U-bolt 22 near the corners thereof and prevent the u-bolt 22 from dropping into the hollow center of the column 4. Immediately ahead of the backing rib 52 are depressed locating surfaces 54 which lie in the same plane as the inner margins of the notches 50 (FIGS. 6-8), and these surfaces bear against the legs and bight portion of the U- bolt 22 and prevent the Ubolt 22 from skewing.

Formed integral with the tapered end portion 36 adjacent to the inner margin of one of the notches 50 is a positioning lug 56 (FIGS. 5-8) which projects rearwardly beyond the back abutment surface 48. The positioning lug 56 is slightly tapered and is positioned at the inner corner one one side of the U-bolt 22 when the U bolt 22 is in place in the tapered end portion 36. Thus. the U-bolt bends around the lug 56. Adjacent the inner margin of the other notch 50, the tapered end portion 36 is provided with a socket 58 of the same size and taper as the positioning lug 56. Like the lug 56, the socket 58 is positioned at the bend in the U-bolt 22, only it is at the corner on the opposite side of the U-bolt 22. Thus, the U-bolt 22 also bends around the socket 58. The positioning lug 50 and the socket 58 are positioned equal distance from the longitudinal centerline of the column half 20 so that when two column halves 20 are placed together back-to-back the positioning lug 56 on one will align with and fit into the socket 58 on the other and vice-versa. Consequently, the U-bolt 22 will bend around the positioning lugs 56 of the two column halves 20, and the lugs 56 will prevent the U-bolt 22 from being withdrawn from tapered end position 36.

Along the upper cross wall 42 the column half 20 is provided with a similar construction for aligning and locating the two column halves 20 and for retaining the upper U-bolt 24 (FIG. 5). In particular, the upper cross wall 42 has notches 60, which are spaced apart such that they will accommodate the threaded legs of the upper U-bolt 24, and behind these notches 60 backing ribs 62 project from the front wall 30. Between the notches 60 and the backing ribs 62 are depressed locating surfaces 64 which are wide enough to accommodate the upper U-bolt 24. Near one of the notches 60, the upper cross wall 42 is provided with a positioning lug 66 which projects outwardly beyond the back abutment surface 48, while a socket 68 is molded into the upper cross wall 42 near the other notch 60. When the column halves 20 are fitted together, the positioning lug 66 of one fits into the socket 68 on the other and vice-versa, so that the upper U-bolt 24 is secured in place between the two halves 20. When so positioned the U-bolt 24 bends around the positioning lugs 66 of the two column halves 20 and its threaded legs project upwardly beyond the flat supporting surface 40 at the upper end of the column 4, while the backing ribs 62 prevent the U-bolt 24 from falling into the hollow interior of the column 4.

The axial bore 46 in the spacer 44 of one of the column halves 20 contains a screw 70 (FIG. 3) which is long enough to project from the inner counterbore to the outer counterbore of the bore 46. The screw 70 in turn threads into and secures an ornamental handle 72 against the outwardly presented surface of the facing wall 30 for that column half 20. The axial bore 46 in the other column half 20 affords access to the head of the screw 70 so that it may be tightened without disassembling the column half 20 on which the ornamental handle 72 is mounted. The outer end of the bore 48 in the other column half 20 is normally closed with a decorative plug 74.

Before the pedestal table A is assembled, the column 4 must be assembled and this is accomplished by first placing the screw 70 in the inner counterbore of the axial bore 46 for the spacer 46 of one of the column halves 20. Thereafter the lower U-bolt 22 is laid against the depressed locating surface 54 of lower cross wall 38 in the column half 20 with the threaded legs of that U- bolt projected through the notches 50 and the ends of the offset or bight portion located against the backing ribs 52. The upper U-bolt 24 is likewise laid against the depressed locating surface 64 of the upper cross wall 42 such that the legs thereof project through the notches 60 and the bight portion lies against the backing rib 62. Once the screw 70 and the U-bolts 22 and 24 are emplaced in one of the column halves 20, the back of the second column half 20 is aligned with and brought against the back of the first column half 20 so that the column halves 20 abut along their back surfaces 48. As the two column halves 20 move into abutment, the positioning lugs 56 and 66 of the first column half 20 enter the sockets 58 and 68, respectively of the second column half 20, while the positioning lugs 56 and 66 of the second column half 20 enters the sockets 58 and 68, respectively; of the first column half 20 (FIG. 4).

Thus, when the column halves 20 abut back-to-back along their back surfaces 48, they are interlocked at the positioning lugs 56 and 66 and the sockets 50 and 68 which receive those lugs. Moreover, when the column halves 20 are so interlocked, the U-bolts 22 and 24 are locked securely in place, although a very limited amount of free motion is afforded for alignment with the bolt holes 12 and 16 in the base 2 and top 6, respectively. In particular, the U-bolts 22 and 24 are prevented from falling into the hollow interior of the column 4, by the backing ribs 52 and 62. The positioning lugs 56 and 66, around which the U-bolts 22 and 24 bend prevent the U-bolts from being withdrawn from the column 4 even when substantial forces are applied to them (FIG. 2). The intervening horizontal portion of the lower cross wall 38 between the lugs 56 further serves to prevent withdrawal of the lower U-bolt 22, while the intervening portion of the upper cross wall 42 further serves to prevent withdrawal of the upper U- bolt 24. The margins of the notches 50 and 60 prevent the U-bolt 22 and 24 from moving in the one transverse direction, while the depressed locating surfaces 54 and 64 prevent them from moving in the other transverse direction. Thus, the notches 50 and 60, the locating surfaces 54 and 64, and the backing ribs 52 and 62 define bolt receiving cavities in which the U-bolts 22 and 24 are captured.

After the two column halves 20 have been interlocked with their backs abutting and the U-bolts 22 and 24 captured therein. staples 76 (FIG. 3) are driven through the lower cross wall 38 at the locations of the lugs 56 and sockets 58 therein and more staples 76 are driven through the upper cross wall 42 at the location of the lugs 66 and socket 68 therein. These staples may bridge the parting line at the abutting back surfaces 48 and furthermore are long enough to enter the sockets 58 and 68 and lodge in the lugs 56 and 66 fitted into those sockets. Hence, the staples 76 hold the column halves 20 firmly together.

Next the column 4 is painted. Finally, the ornamental handle 72 is installed by placing it against the outside face of the front wall 30 at the proper location and turning the screw 70. Access to the head of the screw 70 is obtained through the bore 46 of the other column half 20. Once the handle 72 is secured, the decorative plug 74 is pressed into the bore 46 of that other column half 20.

The table A is usually shipped in a knocked down condition and assembled by the user. The assembly is quite simple, involving nothing more than inserting the tapered end portion 36 of the column 4 into the upwardly opening socket of the base 2, in which case the threaded legs of the lower U-bolts 22 will pass through the bolt holes 12 in the bottom wall of the socket I0. The nuts 26 are then threaded over the U- bolts 22 to secure the column 4 to the base 2. As the nuts 26 are tightened, the bight portion of the U-bolt 22 bears against the lugs 56 around which it is bent, as well as against the intervening portion of the lower cross wall 38 between the lugs 56 (FIG. 2). Next the top 6 is positioned over the column 4 with its bolt holes 16 aligned with the threaded legs on the upper U-bolt 24. As the top 6 is lowered the legs of the U-bolt 24 pass into the bolt holes 16 and the underside of the top 6 comes to rest against the flat supporting surface 40 in the upper end of the column 9. Then the flanged nuts 28 are inserted into the bolt holes 16 and threaded over the threaded legs of the U-bolt 24 to secure the top 6 at the column 4. Again, the bight portion of the upper U-bolt 24 bears against the lugs 66 as well as the intervening portion of the upper cross wall 42 between those lugs 66 to prevent the U-bolts from pulling out of the column 4 (FIG. 2).

MODIFICATIONS A modified column, which is somewhat narrower than the column 20 and as a result possesses a slightly different construction, consists of a pair of identical column halves 82 (FIGS. 9 & l0), and the upper end of each column half 82 is, apart from external appearance, practically the same as the upper end of the column half 20. The column half 82 has a front wall 84 and half side walls 86 with the walls 84 and 86 terminating at a shoulder 88 from which an end portion 90 of semi-circular cross section projects. Midway be tween its ends one of the side walls 86 is provided with a positioning lug 92 (FIG. 9) and likewise immediately above the shoulder 88 the same side wall 86 is provided with another positioning lug 94. The other side wall 86 has sockets 96 and 98 which are positioned directly opposite the lugs 92, 94 respectively, and are sized and positioned to receive such lugs 94 on the other column half 82.

The end portion 90 is traversed by a cross wall 100 having a positioning lug 102 projecting therefrom and a locating socket 104 set into it adjacent to the axial centerline thereof. The socket 104 is sized to receive this lug 102 of the other column half 82. The surface of the end portion 90 is depressed from the parting line along the sides of the lug 102 and the socket 104 to form a depressed locating surface 105 against which a lower U-bolt 106 is positioned. The U-bolt 106 wraps around the lug 102 and socket 104 and is prevented from moving upwardly by backing ribs or surfaces I08.

To further rigidify the column 80, each column half 82 thereof has a center web 110 extending longitudinally through it from its upper cross wall 42 to its lower cross wall 100. The web 110 is formed integral with the front wall 84.

The column 80 is likewise held together by staples 76, but the lowermost staples are driven through the shoulder 88 instead of through the lower cross wall 100. The legs of the staples 76 embed in the positioning lugs 102 of the column halves 82.

This invention is intended to cover all changes and modifications of the example of the invention herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

l. A structural member for furniture, said structural member comprising: first and second mating sections which fit back to back and abut against each other along abutment surfaces, each section having a locating surface which is depressed relative to the abutment surface on that section, each section further having a lug and a socket, the lug of the first section being projected beyond the abutment surface on that section and into the socket of the second section and the lug of the second section being projected beyond the abutment surface of that section and into the socket of the first section to interlock the sections so they cannot shift transversely or longitudinally with respect to each other. and a connecting U-bolt for attaching the structural member to another component of furniture, the bolt projecting from the sections and having its bight portion extended behind the lugs of the first and second sections so that the lugs will prevent withdrawal of the U- bolt from the abutting sections, the U-bolt lying against the locating surfaces of the first and second sections.

2. A structural member according to claim I wherein the first and second sections are substantially identical.

3. A structural member according to claim I wherein the bight portion of the U-bolt merges into the legs at 90 corners and wherein the lugs are adjacent the insides of those corners.

4. A structural member according to claim I wherein the sections have hollow interiors and at least one of the sections is provided with a backing surface which lies behind the bight portion of the U-bolt and prevents the U-bolt from falling into the hollow interior.

5. A structural member according to claim 4 wherein the depressed locating surfaces lie at least in part between the backing surfaces and the lugs.

6. A structural member according to claim 5 wherein the depressed locating surfaces also lie to the side of each lug.

7. A structural member according to claim 1 wherein on each section the lugs are formed on and the sockets are formed in a cross wall which closes the end of the section, and the cross wall has notches through which the legs of the U-bolt project.

8. [n a pedestal table having a base and a top, an improved column extending between the base and the top for supporting the top in an elevated position, said column comprising: first and second column halves fitted back-to-back and abutting each other along abutment surfaces thereon, each column half at its upper and lower ends having a lug and a socket with the lugs of the one column half being fitted into the sockets of the other column half and vice-versa to interlock the column halves against transverse and longitudinal movement relative to each other; and bolts extended behind the lugs and projected from the ends of the column into the base and top for securing the column to the base and top.

9. The structure according to claim 8 wherein the bolts are U-bolts, the bight portions of which extend behind the lugs.

10. The structure according to claim 9 wherein the U-bolts lie against locating surfaces on each of the column halves with the locating surface of each column half being depressed with respect to the abutment surface of the column half.

1]. The structure according to claim 10 wherein the column halves are injection molded from plastic.

12. A structural member for furniture, said structural member comprising: first and second mating shells which fit together back-to-back and abut each other along abutment surfaces on those shells, each of the shells having at least one lug and a socket with the axes of the lug and socket being oriented generally crosswise with respect to the abutment surface. the lug of the first shell projecting beyond the abutment surface of the first shell and into the socket of the second shell and the lug of the second shell projecting beyond the abutment surface of the second shell and into the socket of the first shell so as to prevent the shells from shifting transversely and longitudinally with respect to each other, the shells when fitted together forming a bolt receiving cavity, a portion of which extends behind and to the side of at least one of the lugs; and a bolt in the bolt receiving cavity, the bolt having a threaded shank located in the portion of the cavity to the side of the lug and projecting beyond ends of the shells, with the shank being oriented generally crosswise with respect to the axis of the lug, the bolt also having an offset portion located in the portion of the cavity behind the lug, whereby the lug cannot be withdrawn from the bolt-receiving cavity.

13. A structural member according to claim 12 wherein the bolt is a U-bolt and the bolt-receiving cavity is located behind and to the sides of the lugs on both shells.

14. A structural member according to claim 12 and further comprising staples which are embedded in both shells and bridge the shells to hold the shells together. 

1. A structural member for furniture, said structural member comprising: first and second mating sections which fit back to back and abut against each other along abutment surfaces, each section having a locating surface which is depressed relative to the abutment surface on that section, each section further having a lug and a socket, the lug of the first section being projected beyond the abutment surface on that section and into the socket of the second section and the lug of the second section being projected beyond the abutment surface of that section and into the socket of the first section to interlock the sections so they cannot shift transversely or longitudinally with respect to each other, and a connecting U-bolt for attaching the structural member to another component of furniture, the bolt projecting from the sections and having its bight portion extended behind the lugs of the first and second sections so that the lugs will prevent withdrawal of the U-bolt from the abutting sections, the U-bolt lying against the locating surfaces of the first and second sections.
 2. A structural member according to claim 1 wherein the first and second sections are substantially identical.
 3. A structural member according to claim 1 wherein the bight portion of the U-bolt merges into the legs at 90* corners and wherein the lugs are adjacent the insides of those corners.
 4. A structural member according to claim 1 wherein the sections have hollow interiors and at least one of the sections is provided with a backing surface which lies behind the bight portion of the U-bolt and prevents the U-bolt from falling into the hollow interior.
 5. A structural member according to claim 4 wherein the depressed locating surfaces lie at least in part between the backing surfaces and the lugs.
 6. A structural member according to claim 5 wherein the depressed locating surfaces also lie to the side of each lug.
 7. A structural member according to claim 1 wherein on each section the lugs are formed on and the sockets are formed in a cross wall which closes the end of the section, and the cross wall has notches through which the legs of the U-bolt project.
 8. In a pedestal table having a base and a top, an improved column extending between the base and the top for supporting the top in an elevated position, said column comprising: first and second column halves fitted back-to-back and abutting each other alonG abutment surfaces thereon, each column half at its upper and lower ends having a lug and a socket with the lugs of the one column half being fitted into the sockets of the other column half and vice-versa to interlock the column halves against transverse and longitudinal movement relative to each other; and bolts extended behind the lugs and projected from the ends of the column into the base and top for securing the column to the base and top.
 9. The structure according to claim 8 wherein the bolts are U-bolts, the bight portions of which extend behind the lugs.
 10. The structure according to claim 9 wherein the U-bolts lie against locating surfaces on each of the column halves with the locating surface of each column half being depressed with respect to the abutment surface of the column half.
 11. The structure according to claim 10 wherein the column halves are injection molded from plastic.
 12. A structural member for furniture, said structural member comprising: first and second mating shells which fit together back-to-back and abut each other along abutment surfaces on those shells, each of the shells having at least one lug and a socket with the axes of the lug and socket being oriented generally cross-wise with respect to the abutment surface, the lug of the first shell projecting beyond the abutment surface of the first shell and into the socket of the second shell and the lug of the second shell projecting beyond the abutment surface of the second shell and into the socket of the first shell so as to prevent the shells from shifting transversely and longitudinally with respect to each other, the shells when fitted together forming a bolt receiving cavity, a portion of which extends behind and to the side of at least one of the lugs; and a bolt in the bolt receiving cavity, the bolt having a threaded shank located in the portion of the cavity to the side of the lug and projecting beyond ends of the shells, with the shank being oriented generally crosswise with respect to the axis of the lug, the bolt also having an offset portion located in the portion of the cavity behind the lug, whereby the lug cannot be withdrawn from the bolt-receiving cavity.
 13. A structural member according to claim 12 wherein the bolt is a U-bolt and the bolt-receiving cavity is located behind and to the sides of the lugs on both shells.
 14. A structural member according to claim 12 and further comprising staples which are embedded in both shells and bridge the shells to hold the shells together. 